ABSTRACT
The efficiency of rock as storage is defined by its storativity coefficient which gives the percentage of water available versus the volume of aquifer drained. For confined aquifers, it gives the amount of water gained to the amount of pressure reduction. Aquifers in consolidated or unconsolidated rocks are higher on the storage capacity scale, as due to their larger volume they may be useful for long-term storage. A phreatic aquifer can be found in some parts of the Upper Zone. In most cases however, the elevation of the water table of confined aquifers is lower than that of the piezometric surface of the underlying confined aquifer. The outflow is by seepage to the surface, by evaporation or by outflow into other aquifers and thence into mudflats. The Western Desert of Egypt is bordered to the north by the Mediterranean Sea, and flow occurs mainly from south to north.
